Treatment of nickel(II) and copper(II) complexes of 2(beta)-formyl-meso-tetraphenylporphyrins with strong acid results in intramolecular cyclization involving the carbonyl carbon and the ortho-phenyl position leading to naphthoporphyrin derivatives. However, when electron-releasing groups are present at the m-phenyl positions, a second cyclization occurs involving the 3(beta) position and the ortho position of the adjacent phenyl ring to give an additional fused ring.